1. Field of Invention
The present invention relates in general to forming an impression of a foot for the modeling of footwear and foot appliances. More specifically, the present invention relates to forming a foot impression of a foot in a dynamic state that simulates the gait cycle that occurs in human ambulation.
2 Prior Art
It is desirable to form an impression of the human foot for making molds for footwear and foot-related appliances. It is a difficult task because of the foot's mobility and variety of tissue densities. A testament of this difficulty is the percentage of the population that are ironically intolerant of their footwear and appliances.
In order to provide background information so that the invention may be completely understood and appreciated in its proper context, reference is made to a number of prior art practices and patents as follows:
A common trade practice as taught by Langer Biomechanics Group of 12 E Industry Ct., Deer Park, N.Y. 11729, and others, molds the foot in plaster gauze and a technician holds the foot suspended in a position while the plaster cures. The method does not perform as the present invention because of the potential for inconsistencies in determining a position to hold the foot. Also, there is no weightbearing on the foot, which inherently would change the foot's shape compared to the suspended, non-weightbearing state.
Another common trade practice as marketed by Hersco Arch Products, 138 E 26th St., NYC, N.Y. 10010, and others, is to press the foot in a crystalline foam block that crushes and compresses to the pressures of the foot. The foot can be pressed into the block in a variety of manners, including one simulating the gait cycle; however, the method does not perform as the present invention because the crystalline foam gives way under very slight pressure; therefore, there is no support or resistance. If the foot is held and pressed lightly into the foam, the mold is essentially the same as the Langer suspended method. It likewise shares the faults of the Langer method. If the foot is not held and is allowed to press into the block with full weightbearing, the lack of resistance and support in the crystalline foam will allow the foot to spread into a flattened or incorrect position against the flat surface on which the block is resting.
Denis, U.S. Pat. No. 4,603,024 discloses molding of the foot in a block of modeling clay. The method does not perform as the present invention for the same reasons as Hersco and Langer. Although clay molds differently than crystalline foam, by viscously displacing as opposed to crushing, clay that is in a consistency to mold the foot will show the same faults in molding.
Another common trade practice, as marketed by Peterson Laboratories, One Mill St., Parish, N.Y. 13131, and others, makes an impression of the foot in a thin thermoplastic sheet while standing or being pressed on a foam cushion. The method does not perform as the present invention because compressed foam rubber cells are connected to adjoining cells and distort these adjoining cells, even if there is no direct pressure on the adjoining cells. This distortion creates uneven pressures on the surface of the foot and puts inaccurate contours into the mold. In addition to the inaccurate contours, inconsistencies will result with varied bodyweights on the same cushion.
Another common trade practice as marketed by Superfeet, 1852 Peace Portal Dr., Blaine, Wash. 98239 and N.W. Podiatric Laboratory, 1091 Fir Ave., Blaine, Wash. 98230, makes a mold or impression of the foot in thermoplastic or thermocork sheets or plaster gauze by applying the mold medium to the foot by vacuum-bag suction. The vacuum-bagged foot is then placed in a shoe or against a flat surface and held in a position until the mold medium cures. The method does not perform as the present invention, for the same reasons stated in the Langer case. Also, pressing the foot against a flat surface or shoe distorts the natural contour of the foot.
Another common trade practice as marketed by Riecken Orthotic Lab, 401 N. Green River Rd., Evansville, Ind. 47715, makes a mold of the foot in thermowax sheet by pressing, wiggling and digging the foot and accompanying mold medium into a box of sand. The method does not perform as the present invention, because the motions of the foot that force it into the sand are not normal ambulatory foot motions and create an unnatural and inaccurate contour.
Arefit of 1931 Las Plumas Ave., San Jose, Calif. 95133, computer images an impression of the foot by placing it on a bed of digitally read plunger rods that extend out of a flat surface. This method does not perform as the present invention for the same reasons as stated above for Hersco and Superfeet/N.W. Podiatric. Also, the foot contour is affected by the flat surface.
Foot Image Technology of 1620 SW Overturf, Bend, Oreg. 97702, computer images the foot with an optical image scanner while the foot is placed on a flat glass plate. This method does not perform as the present invention because the foot contour is affected by the flat glass plate. Also, for an image to be converted into a three-dimensional model, or mold, a designer/programmer must interpret the data from the image and convert this into tool paths. This interpretation is subject to error.
Tekscan of 451 D St., Boston, Mass. 02210, computer images the foot with a bed of force sensors placed on a flat surface and read by a computer. The foot may be applied to the bed in any manner, including gaited; however, the method does not perform as the present invention. The bed senses force-variance over the foot's surface, so three-dimensional surfaces are possible to image; however, as in the Foot Image Technology case, a programmer/designer must interpret the force levels into three-dimensional surfaces to create a model or mold. This interpretation is subject to error. Also, the foot contour is affected by its contact surface.
Whatever the precise merits, features and advantages of the above-cited references, none of them achieves or fulfills the purposes of the present invention. None of the above cited references generates a bodyweight supporting, pressure-equalized impression of the foot while it is dynamically functioning in a gait-simulated manner. All of the above cited references are subject to inaccurate impressions because of artificial influences such as designer's misinterpretations, technicians mis-held positions, flat impression or contact surfaces, distorted impression surfaces, over weightbearing or under weightbearing.